A cellular radio access network is a collection of cells that each includes at least one base station capable of transmitting and relaying signals to subscribers' mobile devices. A “cell” generally denotes a distinct area of a cellular network that utilizes a particular frequency or range of frequencies for transmission of data. A typical base station is a tower to which are affixed a number of antennas that transmit and receive the data over the particular frequency. Mobile devices, such as cellular or mobile phones, smart phones, camera phones, personal digital assistants (PDAs) and laptop computers, may initiate or otherwise transmit a signal at the designated frequency to the base station to initiate a call or data session and begin transmitting data.
Cellular service providers convert cellular signals, e.g., Time Division Multiple Access (TDMA) signals, Orthogonal Frequency-Division Multiplexing (OFDM) signals or Code Division Multiple Access (CDMA) signals, received at a base station from mobile devices into Internet protocol (IP) packets for transmission within packet-based networks. A number of standards have been proposed to facilitate this conversion and transmission of cellular signals to IP packets, such as a general packet radio service (GPRS) standardized by the Global System for Mobile Communications (GSM) Association, mobile IP standardized by the Internet Engineering Task Force (IETF), as well as, other standards proposed by the 3rd Generation Partnership Project (3GPP), 3rd Generation Partnership Project 2 (3GGP/2) and the Worldwide Interoperability for Microwave Access (WiMAX) forum.
A typical 3GPP mobile network includes GPRS core circuit-switched and packet-switched networks, a backhaul network, and a number of radio access networks. A backhaul network for the mobile network includes land-based transmission lines, frequently leased by the service provider, to transport mobile data and control traffic between radio access network base stations and the core networks. The backhaul network also includes network devices, such as the radio network controllers (RNCs) of the radio access networks, aggregation devices, and routers.
The core packet-switched network for the mobile network provides access to one or more packet data networks (PDNs), which may include, for example, the Internet, an enterprise intranet, a layer 3 VPN, and a service provider's private network. Various PDNs provide a variety of packet-based data services to mobile devices, such as bulk data delivery, voice over Internet protocol (VoIP), Internet protocol television (IPTV), and the Short Messaging Service (SMS). Service providers are seeing rapid growth in demand for data services, and this trend will continue to accelerate.
In addition to providing access to PDNs, the core packet-switched network for a service provider's mobile network also provides core support services for the packet-based services of the PDNs. Core support services enable and promote efficiency, security, mobility, and accounting for the packet-based services. GPRS support nodes (GSNs) within the core packet-switched network of the mobile network provider distribute the functionality of the core support services among Serving GSNs (SGSNs), which each serve groups of radio access networks that provide the front-end interface to the mobile devices, and Gateway GSNs (GGSNs), which are edge nodes logically located between the core packet-switched network and the PDNs. The SGSNs and GGSNs may perform, for example, authentication, session management, mobility management, compression, encryption, billing, and filtering for a service provider's GPRS core network.